Injection Device

ABSTRACT

The present invention relates to an injection device comprising a medicament container ( 18 ) and a needle attached to said container, means ( 12,72 ) for automatic penetration of the needle, injection of medicament and withdrawal of the needle, comprising the steps of initiating a penetration sequence, followed by an injection sequence and followed by a withdrawal sequence, wherein a previous sequence triggers a subsequent sequence, and wherein said device further comprises a dampening means arranged and designed to dampen the movement of the injection means during the whole injection sequence.

TECHNICAL FIELD

The present invention relates to an injection device and in particularan injector having several automatic functions.

BACKGROUND OF THE INVENTION

There are many injectors on the market where the aim is to have highdegrees of functionality and automatic features, such as in connectionwith penetration, injection, setting of dose, priming and covering ofthe needle after use. At the same time there is a demand on robustness,repeatability and reliability regarding the function, which sometimesmight be difficult to meet when dealing with complex multi functionsinvolving many interacting components. When there further are demands onlow production costs, especially for devices that are to be used onlyonce, the picture becomes even more complex.

There are in the patent literature numerous solutions to injectiondevices, the bulk of which never enter the market due to that they donot meet the demands in one way or the other. There is therefore acontinuous search for solutions that provide the desired functions thatat the same time fulfil the functional and/or economical demands.

Many devices having multi-functions that work in sequence, such as forexample penetration, followed by injection, followed by withdrawal, havea subsequent sequence triggered at the end of a previous sequence, forexample when the needle has reached full penetration depth, theinjection sequence is triggered.

A common design is to have the movement of an action, e.g. an injectionstroke, to trigger a subsequent movement. To facilitate this in a robustway, tolerances has to accounted for and in that a trigger point willmost often have to be set a portion ahead of the absolute end point. Ifreaching the end point it may happen that the displacement of a meansthat is required to trigger the subsequent action may not occur. If, onthe other hand the trigger point is set too early in the stroke, thesubsequent movement may be triggered so the previous action is notcompleted within the required time or sequence. In both cases there is arisk is that an intended action may become faulty or not occur at all.

One attempt to solve this is disclosed in document WO 03/097133discloses a device having a plunger rod arranged in two parts movable toeach other. Between the parts a delay mechanism is arranged as apiston/cylinder arrangement with a small bleed hole for evacuating theair when the parts are pressed together, whereby a delay of the movementof the plunger rod during the injection sequence is intended, whichshould ensure that the medicament container is emptied before the needleis retracted. However, since both penetration and injection areperformed by a common spring acting on the plunger rod, the delaymechanism is working during the whole penetration and injection sequencewhereby there is a pronounced risk that the delay function hasterminated long before the end of the injection sequence is reached.Further, during the injection operation the retraction spring istensioned.

The document GB 2 414 404 describes an injection device having areservoir containing highly viscous damping fluid, one strong drivespring for performing both penetration and injection, a weaker springthat is tensioned by the stronger spring during penetration andinjection for a needle retraction, and a delay means which is intendedto delay the movement of the plunger rod just before the end of aninjection, whereby the plunger rod is released from the drive spring andthe needle is withdrawn from the injection site. The delay meanscomprises two decoupling mechanisms wherein the first decoupling isactivated just before the stopper within the reservoir reaches its endand the second is activated just before the reservoir is emptied. Thedecoupling is however delayed due to the time it takes to empty thereservoir, whereby it is ensured that the remaining contents of acontainer is discharged before the container is released and returned tothe original position. However, since the delay starts to act justbefore the end of the injection there is a pronounced risk that theelastic members of the injection systems, such as rubber compounds orair that by pressure from a plunger rod has become compressed, do nothave the enough time to expand to a relaxed state before the retractionis triggered and thereby causing problems with its functionalityaccuracy and reliability.

The document GB 2 414 404 or GB 2 424 838 or GB 2 396 298 describes aninjection device comprising one strong drive spring means for performingboth needle penetration and injection by acting on a stopper of asyringe, a weaker spring that is tensioned by the stronger spring duringneedle penetration and injection for a needle retraction, a delay meanshaving a reservoir containing highly viscous damping fluid, which isintended to delay the movement of the plunger rod just before the end ofan injection, whereby the plunger rod is released from the drive springand the needle is withdrawn from the injection site. The delay meanscomprises two decoupling mechanisms wherein the first decoupling isactivated just before the stopper within the syringe reaches its end andthe second decoupling is activated just before the reservoir is emptied.The second decoupling is however delayed due to the time it takes toempty the reservoir, whereby it is ensured that the remaining contentsof a container is discharged before the container is released andreturned to the original position. However, since the delay starts toact just before the end of the injection there is a pronounced risk thatthe elastic members of the injection systems, such as rubber compoundsor air that by pressure from a plunger rod has become compressed, do nothave the enough time to expand to a relaxed state before the retractionis triggered and thereby causing problems with its functionalityaccuracy and reliability.

There is thus room for further improvements in the technical area ofinjection devices with a certain amount of automatically and reliableperformed functions.

BRIEF DESCRIPTION OF THE INVENTION

The aim of the present invention is to provide an injector that fulfilsthe demands that are put on such devices regarding functionality,accuracy and reliability and which ensure that specific functions, suchas injection, are fully completed before a subsequent function isinitiated.

According to a main aspect of the invention it is characterized by thefeatures of the independent patent claim. Further advantageous featuresare subject of the dependent claims.

According to a main aspect of the invention it is characterised by aninjection device comprising an elongated housing; a container carrierhaving a medicament container to which a needle is attached; penetrationmeans comprising a decoupling sleeve, a preloaded penetration springmeans capable of acting on said decoupling sleeve and thereby on saidcontainer carrier causing a sliding movement of the container andneedle, and penetration holding means capable of holding saidpenetration spring means in a loaded state; injection means comprising aplunger rod arranged to act on a stopper in said medicament container, apreloaded injection spring means capable of acting on said plunger rodfor displacement of said stopper inside said container, and injectionholding means capable of holding said injection spring means in a loadedstate; withdrawal means comprising a preloaded return spring meansarranged to act on said decoupling sleeve and thereby on said containercarrier, and withdrawal holding means capable of holding said returnspring means in a loaded state; means for initiating a penetrationsequence capable of acting on a penetration trigger means which isarranged on said decoupling sleeve for disconnecting said penetrationholding means; injection trigger means arranged on said decouplingsleeve and capable of disconnecting said injection holding means forinitiating an injection sequence when the decoupling sleeve and theplunger rod have moved to a certain position; and withdrawal triggermeans arranged on said decoupling sleeve and capable of disconnectingsaid withdrawal holding means for initiating a needle withdrawal whensaid plunger rod has moved to a certain position; wherein the devicefurther comprises a dampening means comprising a compartment containinga volume of highly viscous liquid and defined in part by the outersurface of the plunger rod and an inner surface of a cap, wherein saidcompartment is arranged with a passage through which the liquid may beforced only when the injection sequence is initiated, such that thevolume within the compartment decreases as the plunger rod moves withinthe container during the whole injection sequence and thereby creating adampening shear force.

According to another aspect of the invention, the passage ends in theinterior of the plunger rod.

According to yet another aspect of the invention, the passage ends in anannular space created between said plunger rod and the inner surface ofthe medicament container, whereby said highly viscous liquid is capableof creating a dampening shear force.

According to a further aspect of the invention, the means for initiatinga penetration sequence comprises an activation button, a penetrationsleeve, a lockout sleeve and a needle shield wherein said lockout sleeveis arranged and designed to allow said penetration sleeve to interactwith said penetration trigger means for initiating the penetrationsequence after said needle shield is pressed against an injection siteand said push button is manually operated

The advantage with the device according to the present invention is forone that a dampening of the movement of the plunger rod during the wholeinjection sequence ensures that a complete injection is obtained beforea subsequent step, i.e. the withdrawal of the needle, is triggered. Thisprovides an increased reliability regarding complete emptying of themedicament container, without increasing the tolerance and functionaldemands on the interacting components.

The reliability in performing the injection is also increased becausethe withdrawal spring is not affected at all during neither penetrationnor injection, but it rests in its loaded state until the penetrationand injection sequences are completed and those spring means aredecoupled and only after this is the withdrawal activated. This is incontrast with the above mentioned devices which both rely on thewithdrawal spring being tensioned because of the force and the movementof the injection mechanisms. The counter-directed spring forces,together with friction and tolerance miss-match between co-actingcomponents, could result in an uncompleted injection sequence, i.e. thata lesser dose than prescribed is injected.

Because the delaying is performed by highly viscous liquid being pressedthrough a passage, a reliable and controlled function is obtained. Thedelay mechanism is preferably arranged at the front end of the plungerrod, whereby the passage could end in the interior of the plunger rod.However, it is to be understood that the passage may end in other spacesof the injection device, for example in the annular space between theplunger rod and the inner surface of the tubular medicament container.In this way the highly viscous liquid could also act as a dampercreating dampening shear forces.

Grease viscosity and hydraulic diameter, size and shape of the openingof the plunger rod, are main parameters to tune to deliver the intendedand desired functionality, the intended function being to achieve a timedelay at stroke end so that displacement members of the system are nottriggered before desired displacements, such as e.g. delivery of thedrug, have been completed.

The solution provides a cost effective multi-function device comprisinga safe and reliable chain of sequences, thus ensuring that the userreceives a proper dose of medicament each time the device is used.

These and other features and advantages with the present invention willbecome apparent from the following detailed description and thedrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following detailed description, reference will be made to thedrawings, of which

FIG. 1 is a longitudinal cross-section of an injector comprising thepresent invention,

FIGS. 2-3 are exploded views of the injector of FIG. 1,

FIG. 4 shows a detailed view in cross-section of an embodiment of thepresent invention, and

FIGS. 5-9 show different functional steps of the device of FIG. 1.

DETAILED DESCRIPTION OF THE INVENTION

The device according to the figures comprises a generally tubular outerhousing 10. In the front end of the housing, to the right in FIG. 1, agenerally tubular needle shield 12 is arranged slidably in the outerhousing. When in the non-extended position the needle shield is held inplace by protrusions 14 on the outer surface co-operating with ledges(not shown) on the inner surface of the housing. Inside the needleshield in the front area of the device a container carrier 16 isarranged. Inside the container carrier a container 18, containingmedicament, is attached. Container is to be interpreted as comprisingsyringes, cartridges, ampoules and the like. The front end of thecontainer is arranged with attachment means 20 for attaching a needle 22to the container. The rear end of the container is seated with itsflange 24 in a holder 26. Adjacent the holder an injection release ring28 is arranged, which will be described in more detail below. A plunger30 extends into the container with one end adjacent a stopper 32. Therear end of the plunger is surrounded by a decoupling sleeve 34 which issnap-fitted to the container holder. The decoupling sleeve is arrangedwith flexible tongues 36, FIG. 2, where each tongue is arranged withinwardly directed ledges. In the initial state, these ledges arepositioned in a circumferential groove 37 on the plunger 30. The tonguesand ledges are held in this position by the injection release ring 28.Inside the plunger an injection spring 38 is arranged compressed betweena front wall of the plunger 30 and a wall part 42 of the decouplingsleeve 34. The decoupling sleeve is further arranged with outwardlyextending protrusions arranged on flexible arms 44. Abutting theprotrusions is a retraction release ring 46, which will be describedcloser below. A spring 48, hereafter named penetration spring, isarranged between the retraction release ring 46 and a penetration sleeve50. At the front end of the penetration sleeve, a retraction springretainer 52 is snap fitted with the penetration sleeve 50 by outwardlydirected protrusions 54 having a straight part and a ramped part,extending into recesses 56 of the sleeve. Outside the penetration sleevea lockout sleeve 58 is arranged. At the rear part of the lockout sleeve58 recesses 60 are arranged adjacent flexible arms 62 of the penetrationsleeve, which arms are arranged with outwardly extending protrusions 64as well as inwardly extending ledges 66. In the initial position theseledges are in contact with a wall of a circumferential groove 68 on thedecoupling sleeve 34. The upper part of the arms 62 is further arrangedwith inclined surfaces 70. At the upper end of the housing an activationbutton 72 is slidably arranged, having inwardly extending parts 74,which are arranged with inclined surfaces facing the inclined surfaces70 of the arms 62. Further a penetration retraction spring 76 isarranged between the retraction release ring 46 and an annular ledge 78arranged on the decoupling sleeve 34, FIG. 5 b.

According to the invention it is further arranged with a delaymechanism, FIG. 4. It comprises a cap or cover 100 slidably arranged atthe front end of the plunger rod 30. A compartment 102 created by theinterior of the cap and the front surface of the plunger rod is filledwith a highly viscous liquid, such as grease, oil, paste and the like.The front surface of the plunger rod is further arranged with athrough-hole 104 forming a passage between the compartment and theinterior of the plunger rod, the function of which will be explainedbelow.

The device is intended to function as follows. When in the initialposition the needle shield 12 is positioned inside the housing 10 andheld in place by the protrusions 14 acting against the ledge of thehousing, FIG. 1. The device can be delivered with a protective cap 106inserted into the front end of the needle shield surrounding the frontend of the container 18 with its container cap 78. The protective cap isremoved, whereby the container cap is also removed, and a needle 22 isattached to the container. The needle shield 12 is then pushed manuallyforward until the protrusions 14 of the needle shield enter a recess 80on the inner surface of the housing 10, FIG. 5 a. The protrusions havesuch a configuration that they are able to slide over the ledge when theneedle shield is extended but prevent a pushing in of the needle shieldwhen they have entered the recess.

The device is now ready to use. The user places the end of the needleshield 12 against the injection site and presses the push button 72. Thepressing of the needle shield 12 causes it to move a short distanceinwards until the protrusions 14 of the needle shield abut the upperwall of the recess 80. This movement causes the lockout sleeve 58 to bemoved the same short distance since the upper end of the needle shield12 in the extended position is in contact with the lower end of thelockout sleeve 58.

If the device is withdrawn from the injection site the lockout sleeveand the needle shield are moved back to initial position. The movementof the lockout sleeve causes its recesses 60 to be positioned outside ofthe outwardly extending protrusions 64 of the arms 62 of the penetrationsleeve 58, which enables the button 72 to be depressed whereby theinclined surfaces of the inwardly extending parts act on the inclinedsurfaces 70 of the arms 62, causing them to move radially outwards. Thisis not possible when the lockout sleeve 58 has not been moved since theprotrusions of the arms then abut the inner surface of the lockoutsleeve.

When the arms move radially outwards the inwardly directed ledges 66 ofthe arms 62 are moved out of contact with the circumferential groove 68of the decoupling sleeve 34 which then is moved forward by thepenetration spring 48 acting on the retraction release ring 46 which isheld in place relative the decoupling sleeve 34 by the protrusions 44.Thus both the decoupling sleeve 34, the plunger 30 arranged inside theactivation housing, the container carrier 16 connected to the activationhousing, the injection release ring 28 and the container 18 are movedforward causing a penetration of the needle into the injection site,FIG. 6.

At a certain depth the injection release ring 28 is stopped by theengagement of protrusions on its flexible arms into slots on the needleshield 12, which frees the flexible tongues 36 because they pass thering due to the continued movement of the decoupling sleeve 34. Thefreeing of the tongues cause them to flex outwards radially, whereby theinwardly directed ledges are moved out of contact with the groove 37 onthe plunger. The movement of the decoupling sleeve 34, and thus thepenetration, is stopped when the retraction release ring 46 contacts theretraction spring retainer 52.

However the plunger is now free to move by the force of the injectionspring 38, whereby it pushes on the stopper 32 and an injection isperformed, FIG. 7. When the stopper has reached almost the front end ofthe container, the force of the plunger rod will act on the highlyviscous liquid in the compartment 102 inside the cap 100, the forcegenerating a displacement of the cup 100 which in turn makes the grease,or oil, to flow through the passage 104 provided by the tip of theplunger rod, FIG. 4. Grease viscosity and hydraulic diameter, size andshape of the opening of the plunger rod, are main parameters to tune todeliver the intended and desired functionality, the intended functionbeing to achieve a time delay at stroke end so that displacement membersof the system are not triggered before desired displacements, such ase.g. delivery of the drug, have been completed.

The movement of the plunger in relation to the decoupling sleeve 34causes the upper end of the plunger to pass the protrusions 44 of theactivation housing, whereby they are capable of collapsing inwards, FIG.8.

The collapsing causes the retraction release ring 46 to pass theprotrusions 44 and to be pushed downwards by the retraction spring 76.This causes the container carrier 16 with the container 18 to be pulledinto the housing via the decoupling sleeve 34 at near end of injectionstroke, and thus the needle 22 to be retracted, FIG. 9. The injection isnow completed and the needle is protected inside the housing.

The present invention could of course be used for delaying otherfunctions of an injection device such as a delaying mechanism arrangedto delay the movement of the penetration mechanism in order to ascertainthat the penetration is fully completed before the injection istriggered.

It is to be understood that the embodiment described above and shown inthe drawings is to be regarded only as a non-limiting example of theinvention and that it may be modified within the scope of the patentclaims.

1.-4. (canceled)
 5. An injection device, comprising: an elongatedhousing; a container carrier having a medicament container to which aneedle is attached; a penetration mechanism, comprising a decouplingsleeve, a preloaded penetration spring device capable of acting on thedecoupling sleeve and thereby on the container carrier causing a slidingmovement of the container and needle, and a penetration holding deviceconfigured for holding the penetration spring device in a loaded state;an injection mechanism, comprising a plunger rod arranged to act on astopper in the medicament container, a preloaded injection spring deviceconfigured for acting on the plunger rod for displacement of the stopperinside the container, and an injection holding device configured forholding the injection spring device in a loaded state; a withdrawalmechanism, comprising a preloaded retraction spring arranged to act onthe decoupling sleeve and thereby on the container carrier, and awithdrawal holding device configured for holding the retraction springin a loaded state; a penetration sequence initiating mechanismconfigured for acting on a penetration trigger device arranged on thedecoupling sleeve for disconnecting the penetration holding device; aninjection trigger device arranged on the decoupling sleeve andconfigured for disconnecting the injection holding device for initiatingan injection sequence when the decoupling sleeve and the plunger rodhave moved to a certain position; a withdrawal trigger device arrangedon the decoupling sleeve and configured for disconnecting the withdrawalholding device for initiating a needle withdrawal when the plunger rodhas moved to a certain position; and a damping mechanism, comprising acompartment containing a volume of viscous liquid and defined in part byan outer surface of the plunger rod and an inner surface of a cap,wherein the compartment is configured with a passage through which theviscous liquid can be forced only when the injection sequence isinitiated, such that the volume within the compartment decreases as theplunger rod moves within the container during the injection sequence andthereby creating a damping shear force.
 6. The injection device of claim5, wherein the penetration sequence initiating mechanism comprises anactivation button, a penetration sleeve, a lockout sleeve, and a needleshield; the lockout sleeve is arranged to allow the penetration sleeveto interact with the penetration trigger device for initiating thepenetration sequence after the needle shield is pressed against aninjection site and the push button is manually operated.
 7. Theinjection device of claim 5, wherein the passage ends in an interior ofthe plunger rod.
 8. The injection device of claim 7, wherein thepenetration sequence initiating mechanism comprises an activationbutton, a penetration sleeve, a lockout sleeve, and a needle shield; thelockout sleeve is arranged to allow the penetration sleeve to interactwith the penetration trigger device for initiating the penetrationsequence after the needle shield is pressed against an injection siteand the push button is manually operated.
 9. The injection device ofclaim 5, wherein the passage ends in an annular space created betweenthe plunger rod and an inner surface of the medicament container,whereby the viscous liquid is enabled to create a damping shear force.10. The injection device of claim 9, wherein the penetration sequenceinitiating mechanism comprises an activation button, a penetrationsleeve, a lockout sleeve, and a needle shield; the lockout sleeve isarranged to allow the penetration sleeve to interact with thepenetration trigger device for initiating the penetration sequence afterthe needle shield is pressed against an injection site and the pushbutton is manually operated.